The Stepmother

Architect Frank Delgado returns home from a business trip to Mexico, only to find his client Alan Richmond's car in his driveway. Confronting his suspicions of an affair between his wife Margo and Richmond, Frank brutally attacks and kills Richmond, then buries the body on the beach. The next morning, the police receive a report of two bodies found at the beach, while Frank and Margo host a group of friends, including their business partner Dick Hill and his wife Sonya, and a pornographic film director, Goof, and his wife Rita, at the beach house belonging to Richmond, whom they are building a new property for.